Structural Evolution of the SE Margin of the Browse Basin

Abstract

The Browse Basin is an area of increasing production activity on the NW Shelf of Australia, with production planned from the Ichthys and Prelude fields. The development of infrastructure in this remote area increases the attractiveness of exploration, but the basin is relatively little studied compared to more prolific areas of the NW Shelf, such as the Northern Carnarvon Basin. Existing understanding of the structural and stratigraphic evolution of the Browse Basin is largely based on regional 2D seismic profiles, but the increasing availability of public domain 3D seismic data provides the opportunity to develop new insights into basin evolution. The structural fabric of the basin is most likely controlled by NE-SW trending faults of possible Permian or Carboniferous age, evidenced by the deep incision of fault controlled topography on the SE flank of the basin. This controls the orientation of the basin margin fault system, although its relationship to basement structures in the Caswell Sub-basin remains enigmatic, with some segments of the fault appearing to detach on the basement. A phase of Late Triassic/Early Jurassic extension also resulted in the development of prominent NNE trending intra-basin faults, suggesting oblique reactivation of the older structure. The end of this phase of deformation resulted in the development of a prominent angular unconformity which eroded the crest of rotated extensional fault blocks. Interestingly, this also corresponds in time to the enigmatic “Fitzroy Movement”, a supposed episode of basin inversion, although there is no evidence of compressional deformation of this age in the Caswell Sub-basin. Renewed extension during the Early to Middle Jurassic was mainly accommodated on ENE trending faults, suggesting a rotation of the stress field. Passive margin subsidence ensued during the Cretaceous and Palaeogene, with relatively limited evidence of Lower Cretaceous fault reactivation which is more common further to the SW in the Northern Carnarvon Basin. A phase of compression during the Miocene resulted in the development of a NW-SE trending anticline, seemingly independent of underlying extensional structures, but consistent with the present day stress field. This study demonstrates the importance of understating the multi-phase deformation that has affected the Browse Basin, and the implications that this has for the timing of trap formation and potential for seal breaching due to fault reactivation.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015